1. Field of the Invention
The present invention relates to a circuit board assembly and a backlight module, specifically, a circuit board assembly and a backlight module for use in a liquid crystal display (LCD).
2. Descriptions of the Related Art
Liquid crystal displays (LCD) have many advantages, such as low power consumption, low emission, small footprints, light weight, and is the most commonly used display. Therefore, LCDs have found widespread use in electronic products incorporating display screens, such as mobile phones, digital cameras, personal digital assistants (PDAs) and TV sets. However, since the liquid crystal layer of LCDs does not emit light per se, an additional light source is required. Light emitted therefrom has to be manipulated by the pixel liquid crystals and filtered by a color filter before forming an image on the screen. Generally, the additional light source is known as the backlight module.
FIG. 1 depicts the side view of a backlight module 1 using a light emitting diode (LED) as the light source. The backlight module 1 consists of at least one LED 10, a printed circuit board (PCB) 11, a thermo-conductive material 12 and a bezel 13. The LED 10 is disposed on the PCB 11 to receive the current and various control signals from the PCB 11. The thermo-conductive material 12 is disposed beneath the PCB 11 to conduct heat from the PCB 11 to the bezel 13 (typically a metallic bezel). This heat dissipation mechanism for the LED 10 will provide a better color uniformity.
As depicted in FIG. 2, the conventional PCB 11 further comprises a laminate 111 and conductive structures 113 formed on the upper and lower surfaces of the laminate 111 respectively. Usually, a solder-resist layer 115, typically in a green or brown color is further applied on the conductive structures 113 of the PCB 11. The solder-resist layer 115 helps to restrict the soldering tin applied only on the specific regions during the downstream process of soldering the PCB 11. The PCB surface is then protected against pollution, oxidization and short-circuiting during the subsequent soldering and cleaning processes.
However, the conventional solder-resist is made of a material that may retard electro-conduction and thermo-conduction. Although a thermo-conductive material 12 is often applied onto the bottom surface of the PCB 11 in the backlight module 1 of the prior art, the retarding impact exerted by the solder-resist 115 on the thermo-conduction may heavily discount the heat dissipation performance. Eventually, the poor heat dissipation performance of the PCB 11 may lead to uniformity degradation of light provided by the backlight module 1, thus deteriorating the overall quality of the LCD.
Accordingly, it is important to dissipate heat effectively by eliminating the impact of the solder-resist on the PCB of a backlight module that uses an LED as the light source.